1. Technical Field
The present invention relates to a piezoelectric element formed of a lower electrode film, a piezoelectric layer made of a piezoelectric material, and an upper electrode film, to an actuator device including the piezoelectric element which can be flexurally deformed, and also to a liquid-jet head and a liquid-jet apparatus, each using the actuator device.
2. Related Art
As a piezoelectric element used for an actuator device and the like, there is a piezoelectric element in which a piezoelectric layer is sandwiched between two electrodes: lower and upper electrode films. The piezoelectric layer is made of a piezoelectric material, such as a crystallized piezoelectric ceramic, with an electromechanical transduction function. Moreover, as a device using an actuator device including a piezoelectric element, that is, an actuator device of a flexure vibration mode, there is a liquid-jet head that ejects a droplet from a nozzle orifice by utilizing the displacement of the piezoelectric element. A typical example of the liquid-jet head of this type is an ink-jet recording head. In the ink-jet recording head of this type, a part of a pressure-generating chamber, which communicates with a nozzle orifice for ejecting an ink droplet, is formed of a vibration plate. The vibration plate is deformed with a piezoelectric element to pressurize ink in the pressure-generating chamber, so that the ink droplet is ejected from the nozzle orifice.
A piezoelectric element used in an ink-jet recording head and the like may be fabricated in the following manner. Specifically, a piezoelectric layer and an upper electrode film are formed, by using a film-forming technique, over the entire surface of a substrate on which a lower electrode is provided. Then, the piezoelectric layer and the upper electrode film are cut into pieces, each having a shape corresponding to a pressure-generating chamber, by a lithography method, so that a piezoelectric element is formed (see JP-A-11-151815).
Furthermore, a lower electrode film is proposed to have a three-layer structure formed of, for example, an iridium layer, a platinum layer and another iridium layer (see JP-A-2001-274472).
In such a piezoelectric element used in an ink-jet recording head and the like, a problem, such as delamination, may occur when the piezoelectric element is repeatedly driven. In addition, since the lower electrode film has an insufficient rigidity, the characteristic as an electrode may be deteriorated due to the repetitive use.
Such problems exist not only in a piezoelectric element of an actuator device installed in a liquid-jet head such as an ink-jet recording head, but also in a piezoelectric element used in any other kind of device.